PURPOSE: To obtain a high printing durability greater than or equal to aluminum by making as hydrophilic non-image section a hard substance layer mainly composed of copolymer containing acrylamide, an addition polymerizing insaturated carboxylic acid and an addition polymerizing insaturated compound containing an epoxy group as monomer unit.

CONSTITUTION: An acrylamide copolymer is composed of an acrylamide unit, an addition polymerizing insaturated carboxylic acid unit and an addition polymerizing insaturated compound unit as essential component units. The content of the acrylamide is preferably 50mol%, that of the addition polymerizing insaturated carboxylic acid unit and the addition polymerizing insaturated compound unit containing an epoxy group at least 0.5mol%. When the amounts of the addition polymerizing insaturated carboxylic acid unit and the addition polymerizing insaturated compound unit containing an epoxy group is under 0.5mol%, the hardening can not advance sufficiently. The acrylamide copolymer forms a tough film layer due to reaction between the carboxylic group and the epoxy group.